Gas Electron Multipliers

Gas Electron Multipliers have been developed by CERN back in 1996, for purposes of high energy physical experiments.  They are a development of a multiwire proportional chamber, which has been developed by G. Charpak. This invention got him a Nobel Prize in physics back in 1992.

GEM is constructed out of 50 µm foil coated with  5 µm layers of copper, at both sides, with a network of specifically shaped  holes with a diameter of 60-80µm on the surface of the metal and  40-60µm holes in half of the foil’s thickness. The holes have a peculiar hourglass, double-cone shaped cross section. Thanks to that shape, when voltage is applied in between the top and the bottom layer of the foil, the electrical field in the holes achieves strength of up to 50kV/cm, which creates an avalanche of multiplied electrons. TTA Techtra is the only company in Europe which gained a right to use CERN developed technology in order to produce GEM foils.

Typical GEM foils parameters:

  • GEM boards size: 170 x 170 mm
  • GEM active area: 100 x 100 mm
  • Holes diameter in copper: 70μm +/-5μm
  • Holes diameter in Kapton: 50μm +/-5μm
  • Leakage currents: less than 10 nA at 600V @ 30% HR

We produce GEM foils with different parameters  on request.

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Microscopic view of GEM foil. The very first GEM made by TTA Techtra, 2013.
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Real cross section of the GEM foil manufactured by TTA Techtra. Optical inspection of 40x40cm2 GEM foils, TTA Techtra, 2014.
A GEM foil of 120x60cm2 dedicated to Compact Muon Solenoid experiment, TTA Techtra, 2015.